Continuous process of making superphosphate



June 19, 1923.

STATES HYLEMAN, ALISON WEBSTER, OF COLUMBIA, TENNESSEE.

CONTINUOUS PROCESS OI MAKING SUPERPHOSPHATE.

We Drawing.

To all whom it may concern:

Be it known that I, HYLEMAN ALISON Wnesrnn, a citizen of the United States, re sidin at Columbia, in the county of Maury and tate of Tennessee, have invented certain new and useful Improvements in Continuous Processes of Making Superpahosphate; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to a continuous process of making superphosphates from low grade phosphate rock, and has for its object to lessen the cost, and to increase the efliciency of the methods heretofore proposed.

With these and other objects in view, the invention consists in the novel steps and combinations of steps constituting the process, all as will be more fully hereinafter disclosed and particularly pointed out in the.

claims.

In order that the invention may be the more clearly understood, it is said: It is well recognized that in makin what is known commercially as super-p osphates, or products containing a mixture of monocalcium phosphate and di-calcium phosphate, from phosphate rock, it has not prior to this invention been considered practicable to employ agrade of phosphorite containing less than say 70% of tri-calcium phosphate or more than sa oxides combine And it is further well known that it has been found necessary to use for each 1000 pounds of said rock from 900 to 1000 pounds of sulphuric acid of 52 B.

In carrying out this invention, on the other hand, I am enabled to employ a much lower grade of rock than has been found commercially practicable heretofore, and therefore, am enabled to bring into the market large quantities of low grade phosphorite that at present have comparatively little value.

In practice I proceed as follows: The rock is finely subdivided, and the powder thus produced is placed in mixing tanks provided with stirrers, and steam coils for heating said powder. To these tanks are added for each 1000 pounds of rock powder about, 1000 pounds of water, and the mixture stirred to 7 place all particles of rock in suspension. In

5% of iron and aluminum,

Application filed Kay 20, 1922. Serial No. 562,558.

tanks for each 1000 pounds of rock powder there is placed about 600 pounds of E. sulphuric acid, and to each 600 pounds of this acid is added about 1000 pounds of water. i

The dilute acid thus obtained is now transferred as rapidly as possible to the rock powder while the latter still forms the above mentioned suspension in water, so the acid may immediately attack all the suspended particles of rock. But owing to the relatively small quantity of acid, it converts a portion only of the tri-calcium phosphate present into mono-calcium phosphate, CaH,,P,O along with some di-calcium phosphate Ca H P,O The reaction almost immediatel produces in the mixture a colloidal sponge like mass and this mass is left undisturbed for about thirty minutes in order that the reaction may be completed. After; this 1000 pounds of additional water is added to each 1000 ounds of rock present, and the mass stirre The agitation of the mass causes the undissolved particles of the rock powder to be freed from the colloidal mass in the suspension, while the colloidalmatter separates from said articles in the form of a thin emulsion. he surfaces of said undissolved and partially dissolved particles of rock having been thus bared or cleaned from the colloidal matter, the temperature of the mixture, which will be found to be about 30 C. is now raised. When said temperature reaches about 60 C., hydrolysis sets in, and this latter action reaches a maximum activity when the temperature reaches about 85 C.. Artificial heating is now stopped,when it is found that the chemical heat generated will continue to raise the temperature of the mass to usually 92 C. and often as high as to 96 C.

During the hydrolytic action just described, the mono-calcium phosphate, CaH P O present is broken down into dicalcium phosphate, Ca H P,O and calcium pyro-phosphate. Ca. ,P O,, and also into ortho-phosphoric acid, H PO The ortho-phosphoric acid thus produced immediately attacks the suspension or the particles of rock powder left unattacked, or partially attacked, by the original dilute sulphuric acid, and whose surfaces are now clean, or bared as above stated.

This action produces more mono-calcium phosphate and (ii-calcium phosphate, and'it finally results that allthe original tri-calcipitated out with the solids. The

cium phosphate present is converted into soluble phosphates.

quantity of sulphuric acid to each 1000 pounds of rock, than has heretofore been found possible, and still to render available all the phosphate present. This result is attained whether high grade or low grade prosphates are employed, and no matter what may be their content of iron and aluminum oxides. That is, the sulphuric acid is employed in connection with a hydrolytic action to produce ortho-phosplioric acid, and the latter completes the conversion of the in-- soluble, hosphates into the soluble form.

The di-cal'cium phosphate and the calcium pyro-phosphate together with'any calcium sulphate and other impurities present will precipitate out as solids, while the monocalcium phosphate will remain in solution. The solids are separated out by any suitable method such as decantation, or filtration, and are also dried by any suitable and well known means. a a

A second batch of rock powder is next prepared as before, and a second batch of sulphuric acid of 60 B. having been provided, diluted with water and mixed with said powder to produce the colloidal and sponge like mass, andthe mixture-having been allowed to stand for about thirty minutes as before instead of adding an additional quantity of water as in the preceding case, one now adds the solution of mono-calciumphosphate derived from the preceding operation. That is, to this second formed colloidal mass one adds about 1000 pounds of said solution to each 1000 pounds of rock powder in the second batch.

The process using this second batch of material, is now carried on as before and new solids containing di-calcium phosphate precipitated and recovered, and a new solution of mono-calcium phosphate obtained. The recess is thus -made continuous and may be repeated as just outlined on addi-' tional new batches of rock powder as long as one desires. In the treatment of each succeeding batch of rock powder, the solutions of mono-calcium phosphate get more. concentrated and finally become saturated, whereupon mono-calcium phosphate is rei na product, constituting the desired superphosphate, however, always contains a large excess of di-calcium phosphate over the mono-calcium hosphate content. It is dry, free from stic and gummy constituents, will keep in this condition in any climate, and will readily pass through the drills used to spread fertilizers on the soil.

The advantages of the foregoing procedure may be further realized when it is said: This process has an advantage over all others in t at it will make a merchantable That is, I am enabled by this procedure to use a very much less memes standard 16% acid phosphate from a low grade phosphate rock running as low as 00% tri-calcium phosphate, or about 12% below any Tennessee rock now in commercial use. It may even be employed on a rock running as highas 8% or 10% iron and aluminum oxides combined. Under ordinary methods it would be impossible to use such alow grade rock on account of its low content of tri-calcium phosphate and also on account of the hi 'h content of iron and aluminum oxides. in prior methods, the iron and aluminum oxides consume large portions of the sulphuric acid, that would be available for combination with the tri-calcium phosphate were the iron and aluminum oxides not present; and further, the iron and aluminum oxides produce hydroscopic compounds which make against the non-sticky or nonummyphysical conditions desired in the finishedproduct. This present process has a further advantage of yielding a product which can-be shipped the same day it is made, because its physical condition permits of immediate artificial drying, while the products of the prior processes cannot be shipped under periods of from ninety to a hundred days.

It is obvious that those skilled in the art may vary the details of the process without departing from the spirit of the invention. For example, phosphoric, hydrochloric and other acids may be substituted for the sul phuric acid mentioned, and the quantities of each acid varied. Therefore, I do not wish to be limted to the foregoing procedure except as may be required by the claims.

What is claimed is:

1. The process of making superphosphate from phosphorite rock which consists in powdering said rock; suspending said rock powder in water; treating the suspension thus produced with sulphuric acid; diluting with water said suspension after treatment with acid and raising the temperature above 60 C. to bring on a hydrolytic action; and separating out the super-phosphate thus produced, substantially as described.

2. The process of making-super-phosphate from phosphorite rock which consists in powdering said rock; suspending said rock powder in a weight of. water more than one and one half times the weight of said rock; treating the suspension thus produced with a dilute sulphuric acid; leaving the mixture to stand until the action between said rock and acid is substantially complete; diluting with water said suspension after treatment with acid and-raising the temperature above -60 C. to bring on a hydrolytic action; and separating out the super-phosphate solids thus produced, substantially as described.

3. The process of making super-phos hate from phosphate rock which consists in nely intense dividing seid rock to. produce u rock powden; suspending said powder in wnter; s-ddin dilute sulphuric ecid to the suspension tus reduced to to n colloidal moss; adding it ditionelweter to said mess; reising the tempereture of the mixture to shove C. to produce e, hydrolytic action therein; end sepni'eting out the super-phosphate thus reduced substantially as described.

d. in continuous roness of making euper-phosphete from posphute rock which consists in finely dividing seid rock to to n owder; to one portion of seid powder ed ing water to form n suspension; ndding dilutesulphurie acid to said suspension to vpnitinlly decompose the phosphate present;

adding ureter eonteining some mono-celoiuin phosphete to the treeted suspension to iiute the some; reising the tempereture to shove 60 G. to stert n hydrolytic notion in the mixture; and sepemting out the dieelcium phosphate thus formed, suhstuntielly as described,

5. The continuous, prooess of making super-phosphate from hosphute rock which consists in finely dividing seid root: to form n powder; to one portion of sold powder edding water to form n dilute sulphuric acid to seid suspension in a oeentity sucient to only partially decomsuspension; eddingpose the phosphete present; ndding Water conteinin some mono-cnlci phosphete derived i;- n previous operation to the treated susnsion to dilute the some; ruis ing the temperature to shove 60 C. to start it h drolytic notion in the nture; cutting on; the heutwhen seid temperature rises above 80 (3.; end sepereting out the di-cnlcium phosphnte thus formed, suhsten= tislly as described.

6. The continuous process of mnhing super-phosphate from low grade phosphate rook Which'eonsists in finely dividing seid rock to form n gawder; to one portion of said powder edg Wat/8i to form n sus pension; edding dilute sulphuric acid to said suspension in o quentity sucient to only pertielly decompose the phosphete present; adding Water containing some mono-enleium phosphate to the treeted sue pension after the teection hetween the pooh and eeid is complete to dilute the some; ruising the tempereture to shove 80 (1 to start e hydrolytic notion in the mixtuee; and separating out the di-celcium phoe phste thus formed, substentielly es de= scribed.

In testimony whereof l a tune.

HYLEMAN 'ison' WEBSTER,

it 3; they sis 

